1. Field of the Invention
The present invention relates to a CRT (cathode ray tube) display system comprising a CRT having a curved faceplate and a layer of phosphor on one side of the faceplate for producing a display picture through the faceplate and optical means arranged on the other side of the faceplate for re-imaging the display picture to a position in front of the CRT.
2. Description of Related Art
CRTs having curved faceplates carrying a phosphor layer energisable by an electron beam to produce a display picture are, of course, well known. However, because in such devices the display picture is formed on the inside of the faceplate it is not directly accessible for manipulation or processing, for example, for contact imaging or spatial filtering purposes. Previously, some CRTs have utilized fiber optic faceplates to allow photographic film to capture the display picture when placed in contact with the fiber optic faceplate but this approach is very expensive and resolution is limited to the size of the optical fibers.
There have been proposals for non-inverting optical image transfer arrangements for use with CRTs and comprising relatively inexpensive microlens arrays but these devices require the CRT's faceplate to be flat and would not operate satisfactorily if used in conjunction with a curved faceplate. One example of such a device is described in the English--language abstract of JP-A-07077667. This device comprises planar microlens arrays arranged with their planes parallel to one another and the plane of the CRT's flat faceplate. If such a device were to be used with a CRT having a curved faceplate then considerable de-focusing of the image would result, possibly together with multiple images of parts of the display image.